Manufacturing method of butt joint, butt joint, manufacturing method of bent member, and friction stir joining method

ABSTRACT

Two joining members different in high temperature deformation resistance are disposed in an abutted manner. The rotational direction of a probe of a joining member is set to coincide with a rotational direction rotating from the joining member having lower high temperature deformation resistance toward the joining member having higher high temperature deformation resistance. Then, the rotating probe is inserted into the abutting portion of the joining members. The probe is advanced along the abutting portion with the probe inserted in the abutting portion to perform friction stir joining. As a result, a butt joint having high joining strength can be obtained.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application filed under 35 U.S.C. §111(a)claiming the benefit pursuant to 35 U.S.C. § 119(e) (1) of the filingdate of Provisional Application No. 60/470,502 filed on May 15, 2003pursuant to 35 U.S.C. §111(b).

Priority is claimed to Japanese Patent Application No. 2002-198457,filed on Jul. 8, 2002 and U.S. Provisional Patent Application No.60/470,502, filed on May 15, 2003, the disclosure of which areincorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a manufacturing method of a butt jointto be used as a metal member for use in transportation apparatuses,electrical household appliances, industrial machinery or the like, andalso to such a butt joint. The present invention also relates to afriction stir joining (welding) method preferably used for manufacturingthe butt joint and a manufacturing method of a bent member.

BACKGROUND ART

The following description sets forth the inventor's knowledge of relatedart and problems therein and should not be construed as an admission ofknowledge in the prior art.

In this specification, for the explanation purpose, one of the surfacesof joining members in the thickness direction into which a probe of ajoining tool is inserted will be referred to as an “upper surface.”

Friction stir joining belongs to a category of solid welding and hassuch superior advantages that the type of metal members to be joined(welded) is not limited and the joining (welding) causes less distortiondue to thermal stress in accordance with the joining. Therefore, inrecent years, friction stir joining has been used as a joining means formanufacturing various structures.

The friction stir joining will be explained with reference to FIG. 6. InFIG. 6, the reference numeral “51” denotes a flat-shaped metallic firstjoining member and “52” denotes a flat-shaped metallic second joiningmember. The material of the first joining member 51 is different fromthat of the second joining member 52. The thickness t1′ of the firstjoining member 51 is set to be the same as the thickness t2′ of thesecond joining member 52 (i.e., t1′=t2′).

The following explanation will be made on the assumption that the hightemperature deformation resistance Y2′ of the second joining member 2 ishigher than the high temperature deformation resistance Y1′ of the firstjoining member 1 (i.e., Y1′<Y2′).

These two joining members 51 and 52 are disposed such that they areabutted against each other in a manner such that the rear and uppersurfaces thereof are flush with each other, respectively. The abuttingend surface of the first joining member 51 is formed to have unevenportions, and hence gaps 57 are formed at the abutting portion (joiningportion) 53 of these joining members 51 and 52 in a state that both thejoining members 51 and 52 are abutted against each other.

In FIG. 6, the reference numeral “60” denotes a joining tool for use infriction stir joining. This joining tool 60 is provided with a columnarrotor 61 and a pin-shaped probe 62 protruded from the end surface 61 aof the rotor 61. The diameter of the end surface 61 a of the rotor 61 isset to be larger than the diameter of the probe 62.

In order to join the abutting portion 53 of the joining members 51 and52 using the joining tool 60, initially, the rotating probe 62 of thejoining tool 60 is inserted in the abutting portion 53. Then, the probe62 is advanced along the abutting portion 53 with the prove inserted inthe abutting portion 53. By this, the abutted portion 53 will be joined(welded) at the probe inserted portion in accordance with the advancemovement of the probe 62. In FIG. 6, the reference numeral “53′” denotesa joined portion (welded portion) joined (welded) by the probe 62, “55”denotes a friction stir joined portion (friction stir welded portion)formed in the joined portion 53′. “JD′” denotes the joining (welding)direction, which is the same direction as the moving (advancing)direction (MD′) of the probe 62 in this conventional example.

In the friction stir joining, a side of the joining members where therotation direction L of the probe 62 coincides with the joiningdirection JD′ is referred to as an “advancing side,” and the other sidethereof is referred to as a “retreating side.” At the retreating side,fewer frictional heat will be generated. To the contrary, at theadvancing side, since a larger friction amount will be generated in thejoining member, an undercut portion (not shown) will be generated on theupper surface of the friction stir joined portion 55 at the portion ofthe joining member 51 located at the advancing side. In FIG. 6, “AD”denotes the advancing side, and “RE” denotes the retreating side.

In the friction stir joining, when the joining is performed in such amanner that the rotational direction of the probe 12 at the back side ofthe joining direction JD′ coincides with the direction L rotating fromthe second joining member 52 toward the first joining member 51, thefollowing problems will arise.

As explained above, since the amount of frictional heat generated at theretreating side is fewer the second joining member 52 located at theretreating side is hard to be softened. Furthermore, since the secondjoining member 52 has high temperature deformation resistance Y2′ higherthan the high temperature deformation resistance Y1′ of the firstjoining member 51, the second joining member 52 is harder to besoftened. As a result, the rear surface stir region width H′ (the widthof the rear surface of the friction joined portion 55) becomes narrower,which may cause a remain of the gaps 57 at the abutting portion 53. Ifthe gaps 57 remain, the joint strength (e.g., bending strength, tensilestrength) of the butt joint deteriorates. Accordingly, in cases wherethis butt joint is used as, for example, a bending material, the bendingcannot be performed as intended.

The description herein of advantages and disadvantages of variousfeatures, embodiments, methods, and apparatus disclosed in otherpublications is in no way intended to limit the present invention.Indeed, certain features of the invention may be capable of overcomingcertain disadvantages, while still retaining some or all of thefeatures, embodiments, methods, and apparatus disclosed therein.

DISCLOSURE OF INVENTION

The present invention is made in view of the aforementioned technicalbackground.

It is an object of the present invention to provide a manufacturingmethod of a butt joint capable of increasing a rear surface stir regionwidth (a width of a rear surface of a joined portion) and jointstrength.

It is another object of the present invention to provide a butt jointmanufactured by the aforementioned method, a manufacturing method of abent member using the method for manufacturing the butt joint and afriction stir joining method preferably used for manufacturing the buttjoint.

According to the first aspect of the present invention, a manufacturingmethod of a butt joint, includes:

disposing two joining members different in high temperature deformationresistance so as to abut against each other; and

performing friction stir joining by advancing a rotating probe of ajoining tool along an abutting portion of the joining members with therotating probe inserted in the abutting portion, wherein the frictionstir joining is performed in a state in which a rotational direction ofthe probe of the joining tool is set so as to coincide with a rotationaldirection rotating from one of the joining members having a lower hightemperature deformation resistance toward the other of the joiningmembers having a higher high temperature deformation resistance at aback side of a joining direction.

In the first aspect of the present invention, by setting the rotationaldirection of the probe of the joining tool so as to coincide with arotational direction rotating from one of the joining members having alower high temperature deformation resistance toward the other of thejoining members having a higher high temperature deformation resistanceat the back side of the joining direction, the joining member of lowerhigh temperature deformation resistance is located at the treating side.Therefore, the joining member is easily softened, resulting in anincreased rear surface stir region width (i.e., the width of the rearsurface of the joined portion). As a result, even in cases where gapsare formed in the abutting portion of the joining members, the gaps canbe assuredly filled with the materials of the joining members, which inturn can improve the joint strength of the obtained butt joint.Furthermore, since the rear surface stir region width increases, even ifthe probe insertion is not positioned accurately to the abutting portionat the time of joining, the abutting portion can be joined in a goodmanner, resulting in an improved joining operation.

In the present invention, the comparison of the high temperaturedeformation resistance of the joining members is performed based on thedeformation resistance at the joining temperature. Concretely, in caseswhere both the joining members are made of aluminum or its alloy, thecomparison is preferably performed based on the mean deformationresistance within the range of 200 to 600° C., more preferably 400 to550° C. In this case, the rear surface stir region width can beincreased assuredly.

In the present invention, as the joining members, for example, metalmembers can be used. Especially, aluminum or its alloy, cupper or itsalloy can be preferably used.

According to the second aspect of the present invention, a manufacturingmethod of a butt joint, comprises:

disposing two joining members same in material but different inthickness so as to abut against each other with a step formed on uppersurface sides of the joining members; and

performing friction stir joining by advancing a rotating probe of ajoining tool along an abutting portion of the joining members with therotating probe inserted in the abutting portion,

wherein the friction stir joining is performed in a state in which arotational direction of the probe of the joining tool is set so as tocoincide with a rotational direction rotating from one of the joiningmembers having a thinner thickness toward the other of the joiningmembers having a thicker thickness at a back side of a joiningdirection.

In the second aspect of the present invention, by setting the rotationaldirection of the probe of the joining tool so as to coincide with arotational direction rotating from one of the joining members having athinner thickness toward the other of the joining members having athicker thickness at the back side of the joining direction, the thinnerjoining member is positioned at the retreating side, resulting in anincreased rear surface stir region width. Accordingly, the same functionas in the first aspect of the present invention can be obtained.

According to the third aspect of the preset invention, a manufacturingmethod of a butt joint, comprises:

preparing a first joining member of a high temperature deformationresistance Y1 and a thickness t1 and a second joining member of a hightemperature deformation resistance Y2 and a thickness t2; and

performing friction stir joining by advancing a rotating probe of ajoining tool along an abutting portion of the joining members with therotating probe inserted in the abutting portion,

wherein, in cases where the joining members are disposed in an abuttedmanner in a state in which the joining members meet a relation of(Y1×t1)>(Y2×t2), the friction stir joining is performed in a state inwhich a rotational direction of the probe of the joining tool is set soas to coincide with a rotational direction rotating from the secondjoining member toward the first joining member at a back side of ajoining direction, and wherein, in cases where the joining members aredisposed in an abutted manner in a state in which the joining membersmeet a relation of (Y1×t1)<(Y2×t2), the friction stir joining isperformed in a state in which a rotational direction of the probe of thejoining tool is set so as to coincide with a rotational directionrotating from the first joining member toward the second joining memberat the back side of the joining direction.

In the third aspect of the present invention, by setting the rotationaldirection of the probe taking into account of both the high temperaturedeformation resistance and the thickness of the joining members, therear surface stir region width can be increased.

In the first to third aspects of the present invention, it is preferablethat the butt joint is a member to be used as a bending work material.

Furthermore, in the first to third aspects of the present invention, itis preferable that the butt joint is a member to be used as a tailoredblank member for manufacturing automobile parts.

According to the fourth aspect of the preset invention, a butt joint isexcellent in bendability and obtained by the manufacturing methodrecited in any one of the aforementioned first to third aspects of thepresent invention.

With the fourth aspect of the present invention, in the butt jointobtained by the manufacturing method of the butt joint according to oneof the first to third aspects of the present invention, the gaps formedin the abutting portion are assuredly filled with the materials of thejoining members. Therefore, the butt joint is excellent in bendability.As a result, by performing bending operation to the butt joint, thegeneration of bending work defects can be prevented, resulting in a highquality bent member.

According to the fifth aspect of the present invention, a manufacturingmethod of a bent member performs a bending operation to the butt jointobtained by the manufacturing method recited in any one of theaforementioned first to third aspects of the present invention.

With this manufacturing method, a bent member of high quality can beobtained by the same reasons as in the fourth aspect of the presentinvention.

In the fifth aspect of the present invention, the type of bending workis not limited to a specific one, and the bending work can be pressbending work or various bending work using press dies, dies or rolls.

According to the sixth aspect of the present invention, a butt joint isa joint formed by integrally joining two joining members abutted againsteach other by a friction stir joining method, wherein one of the joiningmembers has a high temperature deformation resistance Y1 and a thicknesst1 and the other of the joining members has a high temperaturedeformation resistance Y2 and a thickness t2, and

wherein an undercut portion is formed on a surface of a friction stirjoined portion at a side of one of the joining members having a largervalue of (Y1×t1) or (Y2×t2).

With this butt joint, since the undercut portion is formed on thesurface of the friction stir joined portion at a side of one of thejoining members having a larger value (Y1×t1) or (Y2×t2), less influenceis given to the joint strength by the undercut portion, causing almostno deterioration of the joint strength. Accordingly, the butt joint isexcellent in joint strength.

The butt joint according to the sixth aspect of the present inventioncan be assuredly obtained by the manufacturing method of a butt jointaccording to any one of the first to third aspects of the presentinvention. Furthermore, the butt joint according to the sixth aspect ofthe present invention can be assuredly obtained by the friction stirjoining according to any one of the seventh to ninth aspects of thepresent invention.

In the sixth aspect of the present invention, in cases where undercutportions are formed on the surface of the friction stir joined portionat both sides of the joining member having a larger value of (Y2×t2) andthe joining member having a smaller value of (Y1×t1), it is preferablethat the undercut portion formed on the surface of the friction stirjoined portion at the side of the joining member having the larger valueis relatively larger than the undercut portion formed on the surface ofthe friction stir joined portion at the side of the joining memberhaving the smaller value.

In the sixth aspect of the present invention, it is preferable that thebutt joint is a member to be used as a bending work material.

In the sixth aspect of the present invention, it is preferable that thebutt joint is a member to be used as a tailored blank member formanufacturing automobile parts.

According to the seventh aspect of the present invention, a frictionstir joining method, comprises:

disposing two joining members different in high temperature deformationresistance so as to abut against each other; and

performing friction stir joining by advancing a rotating probe of ajoining tool along an abutting portion of the joining members with therotating probe inserted in the abutting portion,

wherein the friction stir joining is performed in a state in which arotational direction of the probe of the joining tool is set so as tocoincide with a rotational direction rotating from one of the joiningmembers having a lower high temperature deformation resistance towardthe other of the joining members having a higher high temperaturedeformation resistance at a back side of a joining direction.

In the seventh aspect of the present invention, the same function as inthe first aspect of the present invention can be obtained.

According to the eighth aspect of the present invention, a friction stirjoining method, comprises:

disposing two joining members same in material but different inthickness so as to abut against each other with a step formed on surfacesides of the joining members; and

performing friction stir joining by advancing a rotating probe of ajoining tool along an abutting portion of the joining members with therotating probe inserted in the abutting portion,

wherein the friction stir joining is performed in a state in which arotational direction of the probe of the joining tool is set so as tocoincide with a rotational direction rotating from one of the joiningmembers having a thinner thickness toward the other of the joiningmembers having a thicker thickness at a back side of a joiningdirection.

In the eighth aspect of the present invention, the same function as inthe second aspect of the present invention can be obtained.

According to the ninth aspect of the present invention, a friction stirjoining method, comprises:

preparing a first joining member of a high temperature deformationresistance Y1 and a thickness t1 and a second joining member of a hightemperature deformation resistance Y2 and a thickness t2; and

performing friction stir joining by advancing a rotating probe of ajoining tool along an abutting portion of the joining members with therotating probe inserted in the abutting portion,

wherein, in cases where the joining members are disposed in an abuttedmanner in a state in which the joining members meet a relation of(Y1×t1)>(Y2×t2), the friction stir joining is performed in a state inwhich a rotational direction of the probe of the joining tool is set soas to coincide with a rotational direction rotating from the secondjoining member toward the first joining member at a back side of ajoining direction, and

wherein, in cases where the joining members are disposed in an abuttedmanner in a state in which the joining members meet a relation of(Y1×t1)<(Y2×t2), the friction stir joining is performed in a state inwhich a rotational direction of the probe of the joining tool is set soas to coincide with a rotational direction rotating from the firstjoining member toward the second joining member at a back side of thejoining direction.

In the ninth aspect of the present invention, the same function as inthe third aspect of the present invention can be obtained.

The above and/or other aspects, features and/or advantages of variousembodiments will be further appreciated in view of the followingdescription in conjunction with the accompanying figures. Variousembodiments can include and/or exclude different aspects, featuresand/or advantages where applicable. In addition, various embodiments cancombine one or more aspect or feature of other embodiments whereapplicable. The descriptions of aspects, features and/or advantages ofparticular embodiments should not be construed as limiting otherembodiments or the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view of a manufacturing method of a butt jointshowing the state in which a joining operation is in progress accordingto the first embodiment of the present invention;

FIG. 2 is a perspective view showing the state in which bending work isexecuted to the butt joint obtained by the manufacturing method;

FIG. 3 is an explanatory view of a manufacturing method of a butt jointshowing the state in which a joining operation is in progress accordingto the second embodiment of the present invention;

FIG. 4 is an enlarged cross-sectional view taken along the line A-A inFIG. 3;

FIG. 5 is an enlarged cross-sectional view taken along the line B-B inFIG. 3; and

FIG. 6 is an explanatory view of a manufacturing method of a butt jointshowing the state in which a joining operation is in progress accordingto a conventional manufacturing method of a butt joint.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferable embodiments of the present invention will be described indetail with reference to the attached drawings.

FIG. 1 shows an explanatory view showing the manufacturing method of abutt joint according to the first embodiment of the present invention.

In FIG. 1, the reference numeral “1” denotes a plate-like first joiningmember, “2” denotes a plate-like second joining member.

Hereinafter, it is assumed that the high temperature deformationresistance of the first joining member 1 is “Y1,” and the thickness is“t1.” Also, it is assumed that the high temperature deformationresistance of the second joining member 2 is “Y2,” and the thickness is“t2.”

In the first embodiment, the thickness t1 of the first joining member 1and the thickness t2 of the second joining member 2 are set to be thesame (i.e., t1=t2).

On the other hand, the material of the first joining member 1 and thatof the second joining member 2 are different from each other.Accordingly, the high temperature deformation resistance Y1 of the firstjoining member 1 and the high temperature deformation resistance Y2 ofthe second joining member 2 are different from each other (i.e., Y1≠Y2).In detail, the high temperature deformation resistance Y2 of the secondjoining member 2 is set to be higher than the high temperaturedeformation resistance Y1 of the first joining member 1 (i.e., Y1<Y2).

As a result, when the product (Y1×t1) of the high temperaturedeformation resistance Y1 of the first joining member 1 and thethickness t1 is compared with the product (Y2×t2) of the hightemperature deformation resistance Y2 of the second joining member 2 andthe thickness t2, the value of (Y2×t2) is larger than that of (Y1×t1)(i.e., (Y1×t1)<(Y2×t2)).

In this first embodiment, the first joining member 1 and the secondjoining member 2 are made of aluminum or its alloy different from eachother in material.

These two joining members 1 and 2 are disposed in such a manner thatcorresponding end surfaces of the joining members 1 and 2 are abuttedagainst each other with their rear surfaces and upper surfaces flushwith each other, respectively. In this abutted state, both the joiningmembers 1 and 2 are supported by a supporting member (not shown) fromtheir rear surfaces. Furthermore, on the rear surface of the abuttingportion 3 of these joining members 1 and 2, a backing member (not shown)is attached.

At least one of the joining members 1 and 2 (in the embodiment shown inFIG. 1, the first joining member 1) has an uneven abutting end surfacegenerated by the cutting processor the like. Therefore, in the state inwhich both the joining members 1 and 2 are abutted against each other,gaps 7 due to the uneven abutting end surface are formed at the abuttingportion 3 of the joining members 1 and 2. In FIG. 1, please note thatthe gaps 7 are shown with exaggeration for the purpose of illustration.

In FIG. 1, the reference numeral “10” denotes a joining tool forfriction stir joining. This tool 10 is provided with a columnar rotor 11and a pin-shaped probe 12 protruded from the end surface 11 a of therotor 11. The diameter of the end surface 11 a of the rotor 11 is set tobe larger than the diameter of the probe 12. The rotor 11 and the probe12 are made of heat-resistant material which is harder than both thejoining members 1 and 2 and capable of resisting frictional heat whichwill be generated during the joining processing. On the external surfaceof the probe 12, stirring protrusions (not shown) for stirring thematerials of the joining members 1 and 2 softened by frictional heat areformed in a spiral manner.

In this joining tool 10, at least the external peripheral end portion ofthe rotor 11 exists on the plane perpendicular to the rotational axis P.In this embodiment, the end surface 11 a of the rotor 11 is formed intoa flat shape. In the present invention, however, the end surface 11 a ofthe rotor 11 can be formed into a concave shape inwardly dented from theexternal end periphery to the rotational central portion.

Next, a method for joining the abutting portion 3 of the joining members1 and 2 using the joining tool 10 will be explained. In this embodiment,a butt joint 20 to be obtained by this method will be subjected to abending work (see FIG. 2). Concretely, the butt joint 20 can be used asa tailored blank member for manufacturing various automobile parts(e.g., door inner panels, flames, pillars, automobile bodies). In thepresent invention, however, the butt joint 20 is not limited to a memberused as a bending work material or a tailored blank material.

Initially, as shown in FIG. 1, the rotor 11 and the probe 12 of thejoining tool 10 are rotated about the center of the rotational axis P inthe predetermined rotational direction (this rotational direction willbe detailed later). Then, the rotating probe 12 is inserted into theabutting portion 3 of the joining members 1 and 2 from the upper surfacesides thereof. Furthermore, the end surface 11 a of the rotor 11 isdisposed so as to be pressed on the surface of the joining members 1 and2. The insertion of the probe 12 into the abutting portion 3 can beperformed from one longitudinal end of the joining members 1 and 2.

From this state, the probe 12 is advanced along the abutting portion 3of the joining members 1 and 2. In accordance with this advancemovement, the abutting portion 3 of the joining members 1 and 2 at theprobe insertion portion will be joined (welded) sequentially along theabutting portion 3 by the probe 12. In FIG. 1, the reference numeral“3′” denotes an abutting portion joined (welded) by the probe 12, and“5” denotes a friction stir joined (welded) portion formed at theabutting portion 3′. “MD” denotes the moving (traveling) direction ofthe probe 12. In this embodiment, the moving direction MD of the probe12 coincides with the joining direction “JD.”

Now, the rotational direction of the prove 12 of the joint tool 10 willbe explained.

In this embodiment, as mentioned above, the joining members 1 and 2 aredisposed in an abutted manner in the condition in which the relationalexpression of (Y1×t1)<(Y2×t2) is met. Therefore, the rotationaldirection of the probe 12 at the behind of the joining direction JD isset to the rotational direction rotating from the first joining member 1toward the second joining member 2. Then, while rotating the rotor 11and the probe 12 in the rotational direction R, the probe 12 is insertedinto the abutting portion 3 of the joining members 1 and 2.Subsequently, the probe 12 is advanced along the abutting portion 3.

As a result, by the friction heat generated due to the rotation of theprobe 12 and the friction heat generated by the friction between the endsurface 11 a of the rotor 11 and the upper surfaces of the joiningmembers 1 and 2, the joining members 1 and 2 are softened at the probeinsertion portion and its vicinity. The softened material of the joiningmembers 1 and 2 is stirred by the rotational force of the probe 12.Then, the softened material goes around the probe 12 to fill the grooveformed by the advancing probe 12 and solidifies quickly by releasing thefrictional heat. This phenomena is sequentially repeated in accordancewith the advance movement of the probe 12, thereby joining the joiningmembers 1 and 2 along the probe traveling portion, which causes anintegral joint of the joining members 1 and 2.

In the aforementioned friction stir joining method, the first joiningmember 1 is disposed at the retreating side RE, and the value of (Y1×t1)of the first joining member 1 is smaller than the value of (Y2×t2) ofthe second joining member 2 (i.e., (Y1×t1)<(Y2×t2)) as mentioned above.Accordingly, the first joining member 1 can be softened easier than thesecond joining member 2. As a result, the rear surface stir region widthH (i.e., the width of the rear surface of the joined portion 5)increases. Therefore, the gaps 7 generated at the abutting portion 3 ofthe joining members 1 and 2 can be assuredly filled with the materialsof the joining members 1 and 2. Thus, the butt joint 20 obtained by theaforementioned manufacturing method has high joint strength.

FIG. 2 is a perspective view showing the butt joint 20 to which U-shapepressing (or V-shaped pressing) was executed by using a known pressmachine. In this embodiment shown in FIG. 2, the butt joint 20 is bentinto a U-shape cross-section (or V-shaped cross-section) along thefriction stir joined portion 5 such that the rear surface of the joinedportion 5 faces towards outside. As mentioned above, in the butt joint20, the gaps 7 generated in the abutting portion 3 are assuredly filledwith the materials of the joining members 1 and 2, and therefore the butjoint has high joint strength. As a result, in cases where U-shapedpress bending is executed against the butt joint 20, no bending defectsuch as cracks will not be generated in the joined portion 5, whichenables to obtain a high quality bent member. Thus, the butt joint 20can be used especially as a tailored blank member for automobiles.

In the present invention, bending is not limited to U-shaped bending (orV-shaped bending), and various bending can be employed.

According to the manufacturing method of this butt joint, since the rearsurface stir region width H can be increased, the joining of theabutting portion 3 can be performed in a good condition without exactlysetting the insertion position of the probe 12 to the abutting portion3. This enables an efficient joining operation.

FIGS. 3 to 5 illustrate a manufacturing method of a butt joint accordingto the second embodiment of the present invention. In these figures, thesame reference numerals as in the first embodiment are allotted to thecorresponding portions. Hereinafter, the differences between the secondembodiment and the first embodiment will be mainly explained.

In this second embodiment, the thickness t1 of the first joining member1 and the thickness t2 of the second joining member 2 are different fromeach other (i.e., t1≠t2). In detail, the thickness t2 of the secondjoining member 2 is set to be thicker than the thickness t1 of the firstjoining member 1 (i.e., t1<t2).

On the other hand, the material of the first joining member 1 and thatof the second joining member 2 are the same (i.e., Y1=Y2).

As a result, when the product (Y1×t1) of the high temperaturedeformation resistance Y1 of the first joining member 1 and thethickness t1 is compared with the product (Y2×t2) of the hightemperature deformation resistance Y2 of the second joining member 2 andthe thickness t2, the value of (Y2×t2) is larger than that of (Y1×t1)(i.e., (Y1×t1)<(Y2×t2)).

In this second embodiment, the first joining member 1 and the secondjoining member 2 are made of aluminum or its alloy of the same material.

These two joining members 1 and 2 are disposed in such a manner thatcorresponding end surfaces of the joining members 1 and 2 are abuttedagainst each other with their rear surfaces flush with each other. Thus,a stepped portion corresponding to the difference of the thickness isformed on the upper surface sides of the joining members 1 and 2. InFIG. 4, the reference numeral “4” denotes the stepped portion, and “4 a”denotes the corner portion of the stepped portion 4.

The remaining structure of these joining members 1 and 2 is the same asthat of the first embodiment. That is, in FIGS. 3 and 4, the referencenumeral “7” denotes a gap formed at the abutting portion 3 of thejoining members 1 and 2.

The structure of the joining tool 10 is the same as in the firstembodiment, and hence the overlapping explanation will be omitted.

Next, a method for joining the abutting portion 3 of the joining members1 and 2 using the joining tool 10 will be explained.

Initially, the rotor 11 and the probe 12 of the joining tool 10 arerotated about the center of the rotational axis P in the predeterminedrotational direction (this rotational direction will be detailed later).Then, the rotating probe 12 is inserted into the abutting portion 3 ofthe joining members 1 and 2 from the upper surface sides thereof withthe rotating probe 12 inclined toward the first joining member side.Furthermore, the end surface 11 a of the rotor 11 is disposed so as tobe pressed on the surface of the joining members 1 and 2. In this secondembodiment, the end surface 11 a of the rotator 11 is disposed so as tobe pressed onto the shoulder portion (see FIG. 4, “2 a”) protrudedupwardly from the abutting portion 3. The insertion of the probe 12 intothe abutting portion 3 can be performed from one longitudinal end of thejoining members 1 and 2. Furthermore, after inserting the probe 12 intothe abutting portion 3, the rotational axis P can be inclined toward thefirst joining member side. Alternatively, without inclining therotational axis P, the aforementioned inclined state can be realized byinclining the joining members 1 and 2.

From this state, the probe 12 is advanced along the abutting portion 3of the joining members 1 and 2. In accordance with this advancemovement, the abutting portion 3 of the joining members 1 and 2 at theprobe insertion portion will be joined (welded) sequentially along theabutting portion 3 by the probe 12.

As a result, by the friction heat generated due to the rotation of theprobe 12 and the friction heat generated by the friction between the endsurface 11 a of the rotor 11 and the shoulder portion 2 a of the secondjoining member 2, the joining members 1 and 2 are softened at the probeinsertion portion and its vicinity. Furthermore, the shoulder portion 2a of the second joining member 2 is pressed by the end surface 11 a ofthe rotor 11 and therefore the surface of the shoulder portion 2 a isplastically deformed into an inclined surface. Due to the plasticdeformation of the shoulder portion 2 a, a part of the material of theshoulder portion 2 a will fill the corner portion 4 a of the steppedportion 4.

The softened material of the joining members 1 and 2 by the frictionheat is stirred by the rotational force of the probe 12 with theshoulder portion 2 a being deformed. Then, the softened material goesaround the probe 12 to fill the groove formed by the advancing probe 12and solidifies quickly by releasing the frictional heat. This phenomenais sequentially repeated in accordance with the advance movement of theprobe 12, thereby joining the joining members 1 and 2 along the probetraveling portion, which causes an integral joint of the joining members1 and 2.

Now, the direction of rotation of the prove 12 of the rotor 10 will beexplained.

In this second embodiment, as mentioned above, the joining members 1 and2 are disposed in an abutted manner in the condition in which therelational expression of (Y1×t1)<(Y2×t2) is met.

Therefore, the rotational direction of the probe 12 at the back side ofthe joining direction JD is set to the rotational direction rotatingfrom the first joining member 1 toward the second joining member 2.Then, while rotating the rotor 11 and the probe 12 in the rotationaldirection R, the probe 12 is advanced along the abutting portion 3 toperform the aforementioned friction stir joining.

In the friction stir joining method, the first joining member 1 isdisposed at the retreating side RE, and the value of (Y1×t1) of thefirst joining member 1 is smaller than the value of (Y2×t2) of thesecond joining member 2 (i.e., (Y1×t1)<(Y2×t2)). Accordingly, the firstjoining member 1 can be softened easier than the second joining member2. As a result, the rear surface stir region width H increases.Therefore, the gaps 7 generated at the abutting portion 3 of the joiningmembers 1 and 2 can be assuredly filled with the materials of thejoining members 1 and 2. Thus, the butt joint 20 obtained by theaforementioned manufacturing method has high joint strength in the samemanner as in the first embodiment. Furthermore, even in cases whereU-shaped press bending (or V-shaped press bending) by using a knownpress machine is executed to the butt joint, almost no forming defaultswill generate at the joined portion 5, which enables a high quality bentmember.

Especially, this manufacturing method of the butt joint has thefollowing superior advantages. That is, as mentioned above, the endsurface 11 a of the rotor 11 of the joining tool 10 is disposed with theend surface inclined toward the first joining member 1 and the endsurface 11 a of the rotor 11 is disposed so as to be pressed on theshoulder portion 2 a of the second joining member 2. Therefore, thesurface of the joined portion 5 is formed into an inclined surfacebridging the upper surface of the first joining member 1 and that of thesecond joining member 2. As a result, even in cases where bendingprocessing is executed to this butt joint, the stress concentration,which tends to be generated at the stepped portion (see FIG. 4, “4”) atthe time of bending, can be decreased. Accordingly, the butt joint isextremely excellent in bending workability. Therefore, in cases wherebending is executed to this butt joint, a bent member having extremelyhigh quality can be obtained.

Furthermore, as shown in FIG. 5, in this but joint, an undercut portion8 is formed at a portion adjacent to the second joining member 2 on thesurface of the joined portion 5. However, since the value of (Y2×t2) ofthe second joining member 2 is larger than the value of (Y1×t1) of thefirst joining member 1, in this butt joint, the undercut portion 8 givesless influence to the joint strength, resulting in almost nodeterioration of the joint strength. Thus, this butt joint maintains thesuperior joint strength. In FIG. 5, the undercut portion 8 isillustrated with exaggeration for the explanation purpose.

Another advantages of the manufacturing method of the butt joint of thissecond embodiment are the same as in the first embodiment, and thereforethe explanation will be omitted.

In the aforementioned manufacturing methods of the first and secondembodiments, both the joining members 1 and 2 are disposed in a statethat the relational expression of (Y1×t1)<(Y2×t2) is satisfied. To thecontrary, however, in cases where the joining members 1 and 2 aredisposed in a state that the relational expression of (Y1×t1)>(Y2×t2) issatisfied, the rotational direction of the probe 12 at the back side ofthe joining direction JD is set so as to coincide with the rotationaldirection rotating from the second joining member 2 toward the firstjoining member 1. This enables to obtain the aforementioned effects. Thejoining method in this case is the same as in the first and secondembodiments, and hence the overlapping explanation will be omitted.

The present invention is not limited to the aforementioned embodiments,and can be changed in various manners.

For example, in the aforementioned embodiments, the joining of theabutted portion 3 of the first and second joining members 1 and 2 isperformed by advancing the rotating probe 12 inserted in the abuttingportion 3 from the upper surface side of the joining members 1 and 2with the first and second joining members 1 and 2 fixed. In the presentinvention, however, the joining of the abutted portion 3 of the firstand second joining members 1 and 2 can be performed by advancing thefirst and second joining members 1 and 2 against the rotating probe 12with the rotating probe 12 inserted in the abutting portion 3 from theupper surface side of the joining members 1 and 2 fixed. In this case,the direction opposite to the advancing direction of the joining members1 and 2 is the joining direction.

Next, concrete examples and reference examples will be explained.

EXAMPLE 1

A flat plate-shaped aluminum alloy first joining member(JIS-A6061-T6,thickness t1=2 mm) and a flat plate-shaped aluminum alloy second joiningmember (JIS-A5083-O, thickness t2=2 mm) were prepared.

It is generally known that the mean deformation resistance of A6061-T6in the temperature range of 400 to 550° C. is lower than that of A5083-Oin the same temperature range. Accordingly, in the aforementionedtemperature range, the product of the high temperature deformationresistance Y1 and the thickness T1 of the first joining member 1, i.e.,the value (Y1×t1), is smaller than the product of the high temperaturedeformation resistance Y2 and the thickness t2 of the second joiningmember 2, i.e., the value (Y2×t2) (i.e., (Y1×t1)<(Y2×t2)).

On the other hand, as a joining tool 10, a joining tool having an endsurface 11 a of a rotor 11 whose diameter is 12 mm and a probe 12 havinga diameter of 5 mm was prepared.

The aforementioned joining members 1 and 2 were disposed in an abuttedmanner with the rear surfaces thereof and the upper surfaces thereofflush with each other, respectively. Then, the rotational direction ofthe rotor 11 of the joining tool 10 and that of the probe 12 were set soas to coincide with the rotational direction R rotating from the firstjoining member 1 toward the second joining member 2 at the back side ofthe joining direction JD. Then, in accordance with the joiningprocedures shown in the first embodiment, the abutting portion 3 of thejoining members 1 and 2 was joined.

Accordingly, in this example 1, the first joining member 1 was locatedat the retreating side RE and the second joining member 2 was located atthe advancing side.

COMPARATIVE EXAMPLE 1

The rotational direction of the rotor 11 of the joining tool 10 and thatof the probe 12 were set so as to coincide with the rotational directionrotating from the second joining member 2 toward the first joiningmember 1 at the back side of the joining direction JD, and the abuttingportion 3 of the first joining member 1 and the second joining member 2was joined. The other joining conditions were the same as in the example1.

Accordingly, in this comparative example 1, the second joining member 2was located at the retreating side RE and the first joining member 1 waslocated at the advancing side.

EXAMPLE 2

A flat plate-shaped aluminum alloy first joining member(JIS-A5052-O,thickness t1=1 mm) and a flat plate-shaped aluminum alloy second joiningmember (JIS-A5052-O, thickness t2=2 mm) were prepared.

Since the material of the first joining member 1 and that of the secondjoining member 2 are the same, the value (Y1×t1) of the first joiningmember 1 was smaller than the value of (Y2×t2) (i.e., (Y1×t1)<(Y2×t2)).

The aforementioned joining members 1 and 2 were disposed in an abuttedmanner with the rear surfaces thereof flush with each other. Then, therotational direction of the rotor 11 of the joining tool 10 and that ofthe probe 12 were set so as to coincide with the rotational direction Rrotating from the first joining member 1 toward the second joiningmember 2 at the back side of the joining direction JD. Then, inaccordance with the joining procedures shown in the second embodiment,the abutting portion 3 of the joining members 1 and 2 was joined. As thejoining tool, the same joining tool as in the first embodiment was used.

Accordingly, in this second example 2, the first joining member 1 waslocated at the retreating side RE and the second joining member 2 waslocated at the advancing side.

COMPARATIVE EXAMPLE 2

The rotational direction of the rotor 11 of the joining tool 10 and thatof the probe 12 were set so as to coincide with the rotational directionrotating from the second joining member 2 toward the first joiningmember 1 at the back side of the joining direction JD, and the abuttingportion 3 of the first joining member 1 and the second joining member 2was joined. The other joining conditions were the same as in the example2.

Accordingly, in this comparative example 2, the second joining member 2was located at the retreating side RE and the first joining member 1 waslocated at the advancing side.

[Joined Results]

Each rear surface stir region width H of each of the butt jointsobtained by the example 1, the comparative example 1, the example 2 andthe comparative example 2 was measured. These results are shown inTable 1. TABLE 1 Rear surface Retreating side Advancing side stir regionMaterial Thickness Material Thickness width H Example 1 A6061-T6 2 mmA5058-O 2 mm 3.1 mm Comp. A5083-O 2 mm A6061-T6 2 mm 2.5 mm Example 1Example 2 A5052-O 1 mm A5052-O 2 mm 3.8 mm Comp. A5052-O 2 mm A5052-O 1mm 3.0 mm Example 2

As shown in Table 1, the rear surface stir region width H of each of thebutt joints obtained Example 1 and Example 2 is larger than that of eachof the butt joints obtained Comparative Example 1 and ComparativeExample 2. Accordingly, it is confirmed that the manufacturing method ofthe butt joint according to the present invention can increase the rearsurface stir region width H.

Furthermore, although U-shaped press is executed to the respective buttjoints obtained in Example 1 and Example 2, no working defect wasgenerated, and a high quality bent member was obtained.

The effects of the present invention can be summarized as follows.

According to the first aspect of the present invention, since thefriction stir joining is performed with the rotational direction of theprobe of the joining tool coincided with the predetermined direction,the rear surface stir region width (rear surface width of the joinedportion) can be increased. Therefore, even in cases where gaps areformed in the abutting portion of the joining members, the gaps can beassuredly filled with the materials of the joining members, which inturn can improve the joint strength of the butt joint. Furthermore,since the rear surface stir region width can be increased, even if theprobe insertion is not correctly positioned to the abutting portion atthe time of joining, the abutting portion can be joined in a goodmanner, resulting in efficient joining operation.

According to the second aspect of the present invention, the sameeffects as in the first aspect of the present invention can be obtained.

According to the third aspect of the present invention, since therotational direction of the probe is set in view of both the hightemperature deformation resistance and the thickness of the joiningmembers, the rear surface stir region width can be increased assuredly.Accordingly, the joining strength of the butt joint can be increasedassuredly, and the joining operation can be performed more efficiently.

According to the fourth aspect of the present invention, the generationof bending work defects can be prevented assuredly, causing a highquality bent member.

According to the fifth aspect of the present invention, a high qualitybent member can be obtained.

According to the sixth aspect of the present invention, an undercutportion is formed at the portion of the joining member whose product ofY1(Y2) and t1(t2) is larger than the product of Y2(Y1) and t2(t1) of theother joining member on the friction stir joint surface, there is lessinfluence to the joining strength due to the undercut portion, causingless deterioration of the joining strength. As a result, a butt jointhaving excellent joint strength can be provided.

According to the seventh aspect of the present invention, the sameeffects as in the first embodiment can be obtained.

According to the eighth aspect of the present invention, the sameeffects as in the second embodiment can be obtained.

According to the ninth aspect of the present invention, the same effectsas in the third embodiment can be obtained.

While illustrative embodiments of the present invention have beendescribed herein, the present invention is not limited to the variouspreferred embodiments described herein, but includes any and allembodiments having modifications, omissions, combinations (e.g., ofaspects across various embodiments), adaptations and/or alterations aswould be appreciated by those in the art based on the presentdisclosure. The limitations in the claims are to be interpreted broadlybased the language employed in the claims and not limited to examplesdescribed in the present specification or during the prosecution of theapplication, which examples are to be construed as non-exclusive. Forexample, in the present disclosure, the term “preferably” isnon-exclusive and means “preferably, but not limited to.”Means-plus-function or step-plus-function limitations will only beemployed where for a specific claim limitation all of the followingconditions are present in that limitation: a) “means for” or “step for”is expressly recited; b) a corresponding function is expressly recited;and c) structure, material or acts that support that structure are notrecited.

Industrial Applicability

The method for manufacturing the butt joint according to the presentinvention can be used in manufacturing a metal member for use intransportation apparatuses, electrical household appliances, industrialmachinery or the like. The butt joint can be preferably used as such ametal member.

1. A manufacturing method of a butt joint, comprising: disposing twojoining members different in high temperature deformation resistance soas to abut against each other; and performing friction stir joining byadvancing a rotating probe of a joining tool along an abutting portionof the joining members with the rotating probe inserted in the abuttingportion, wherein the friction stir joining is performed in a state inwhich a rotational direction of the probe of the joining tool is set soas to coincide with a rotational direction rotating from one of thejoining members having a lower high temperature deformation resistancetoward the other of the joining members having a higher high temperaturedeformation resistance at a back side of a joining direction.
 2. Amanufacturing method of a butt joint, comprising: disposing two joiningmembers same in material but different in thickness so as to abutagainst each other with a step formed on upper surface sides of thejoining members; and performing friction stir joining by advancing arotating probe of a joining tool along an abutting portion of thejoining members with the rotating probe inserted in the abuttingportion, wherein the friction stir joining is performed in a state inwhich a rotational direction of the probe of the joining tool is set soas to coincide with a rotational direction rotating from one of thejoining members having a thinner thickness toward the other of thejoining members having a thicker thickness at a back side of a joiningdirection.
 3. A manufacturing method of a butt joint, comprising:preparing a first joining member of a high temperature deformationresistance Y1 and a thickness t1 and a second joining member of a hightemperature deformation resistance Y2 and a thickness t2; and performingfriction stir joining by advancing a rotating probe of a joining toolalong an abutting portion of the joining members with the rotating probeinserted in the abutting portion, wherein, in cases where the joiningmembers are disposed in an abutted manner in a state in which thejoining members meet a relation of (Y1×t1)>(Y2×t2), the friction stirjoining is performed in a state in which a rotational direction of theprobe of the joining tool is set so as to coincide with a rotationaldirection rotating from the second joining member toward the firstjoining member at a back side of a joining direction, and wherein, incases where the joining members are disposed in an abutted manner in astate in which the joining members meet a relation of (Y1×t1)<(Y2×t2),the friction stir joining is performed in a state in which a rotationaldirection of the probe of the joining tool is set so as to coincide witha rotational direction rotating from the first joining member toward thesecond joining member at a back side of a joining direction
 4. Themanufacturing method of a butt joint according to claim 1, wherein thebutt joint is a member to be used as a bending work material.
 5. Themanufacturing method of a butt joint according to claim 1, wherein thebutt joint is a member to be used as a tailored blank member formanufacturing automobile parts.
 6. A butt joint excellent in bendabilityobtained by the manufacturing method recited in claim
 1. 7. Amanufacturing method of a bent member which performs a bending operationto the butt joint obtained the manufacturing method recited in claim 1.8. A butt joint formed by integrally joining two joining members abuttedagainst each other by a friction stir joining method, wherein one of thejoining members has a high temperature deformation resistance Y1 and athickness t1 and the other of the joining members has a high temperaturedeformation resistance Y2 and a thickness t2, and wherein an undercutportion is formed on a surface of a friction stir joined portion at aside of one of the joining members having a larger value (Y1×t1) or(Y2×t2).
 9. The butt joint as recited in claim 8, wherein the butt jointis a member to be used as a bending work material.
 10. The but joint asrecited in claim 8, wherein the butt joint is a member to be used as atailored blank member for manufacturing automobile parts.
 11. A frictionstir joining method, comprising: disposing two joining members differentin high temperature deformation resistance so as to abut against eachother; and performing friction stir joining by advancing a rotatingprobe of a joining tool along an abutting portion of the joining memberswith the rotating probe inserted in the abutting portion, wherein thefriction stir joining is performed in a state in which a rotationaldirection of the probe of the joining tool is set so as to coincide witha rotational direction rotating from one of the joining members having alower high temperature deformation resistance toward the other of thejoining members having a higher high temperature deformation resistanceat a back side of a joining direction.
 12. A friction stir joiningmethod, comprising: disposing two joining members same in material butdifferent in thickness so as to abut against each other with a stepformed on upper surface sides of the joining members; and performingfriction stir joining by advancing a rotating probe of a joining toolalong an abutting portion of the joining members with the rotating probeinserted in the abutting portion, wherein the friction stir joining isperformed in a state in which a rotational direction of the probe of thejoining tool is set so as to coincide with a rotational directionrotating from one of the joining members having a thinner thicknesstoward the other of the joining members having a thicker thickness at aback side of a joining direction.
 13. A friction stir joining method,comprising: preparing a first joining member of a high temperaturedeformation resistance Y1 and a thickness t1 and a second joining memberof a high temperature deformation resistance Y2 and a thickness t2; andperforming friction stir joining by advancing a rotating probe of ajoining tool along an abutting portion of the joining members with therotating probe inserted in the abutting portion, wherein, in cases wherethe joining members are disposed in an abutted manner in a state inwhich the joining members meet a relation of (Y1×t1)>(Y2×t2), thefriction stir joining is performed in a state in which a rotationaldirection of the probe of the joining tool is set so as to coincide witha rotational direction rotating from the second joining member towardthe first joining member at a back side of a joining direction, andwherein, in cases where the joining members are disposed in an abuttedmanner in a state in which the joining members meet a relation of(Y1×t1)<(Y2×t2), the friction stir joining is performed in a state inwhich a rotational direction of the probe of the joining tool is set soas to coincide with a rotational direction rotating from the firstjoining member toward the second joining member at the back side of thejoining direction.
 14. The manufacturing method of a butt jointaccording to claim 2, wherein the butt joint is a member to be used as abending work material.
 15. The manufacturing method of a butt jointaccording to claim 3, wherein the butt joint is a member to be used as abending work material.
 16. The manufacturing method of a butt jointaccording to claim 2, wherein the butt joint is a member to be used as atailored blank member for manufacturing automobile parts.
 17. Themanufacturing method of a butt joint according to claim 3, wherein thebutt joint is a member to be used as a tailored blank member formanufacturing automobile parts.
 18. A butt joint excellent inbendability obtained by the manufacturing method recited in claim
 2. 19.A butt joint excellent in bendability obtained by the manufacturingmethod recited in claim
 3. 20. A manufacturing method of a bent memberwhich performs a bending operation to the butt joint obtained themanufacturing method recited in claim
 2. 21. A manufacturing method of abent member which performs a bending operation to the butt jointobtained the manufacturing method recited in claim 3.